Water delivery system and method for making hot water available in a domestic hot water installation

ABSTRACT

A water delivery system is provided, comprising at least one faucet device with a cold water faucet part and a hot water faucet part, a cold water line to the at least one faucet device, a tankless heater device for heating water, a hot water line having a first portion running from an outlet of the tankless heater device to the at least one faucet device and having a second portion running from the at least one faucet device to an inlet of the tankless heater device, and a circulatory pump arranged in the second portion of the hot water line, wherein the circulatory pump has a prefixed first performance level and a prefixed second performance level, wherein the first performance level causes a finite water flow in the hot water line which is below an operation threshold value of the tankless heater device.

BACKGROUND OF THE INVENTION

The present invention relates to a water delivery system.

The present invention further relates to a method for making hot wateravailable in a domestic hot water installation.

A typical water delivery system comprises one or several faucet devices(which are usually arranged at one or several sinks), a cold water lineto the faucet devices and a hot water line to the faucet devices. Hotwater is heated at a heating source. In such a system the problem arisesthat the water “stored” in the hot water line cools down. When a hotwater faucet part is opened, the running water is initially cold waterand only after some time does hot water flow.

As a remedy for this problem it is well known to recirculate hot water.

U.S. Pat. No. 7,832,421 B2, which is incorporated herein, discloses amethod for making hot water available in a domestic water installation,said domestic water installation comprising a source of hot water, ahot-water line and one or more tap connections for hot water connectedto the hot-water line, comprising transporting water from said source ofhot water through that hot-water line, during periods of non-withdrawalthrough that one or more tap connections, such that a temperatureprofile of water in the hot-water line is substantially temporallyconstant and varying spatially monotonically along that hot-water line,wherein the transporting step includes a substantially permanentthroughput of water through the hot water line with at most periodicpause times and said pause times having a length selected to preventcooling of water in the hot-water line.

SUMMARY OF THE INVENTION

In an embodiment of the present invention, a water delivery system isprovided, comprising at least one faucet device with a cold water faucetpart and a hot water faucet part, a cold water line to the at least onefaucet device, a tankless heater device for heating water, a hot waterline having a first portion running from an outlet of the tanklessheater device to the at least one faucet device and having a secondportion running from the at least one faucet device to an inlet of thetankless heater device, and a circulatory pump arranged in the secondportion of the hot water line, wherein the circulatory pump has aprefixed first performance level and a prefixed second performancelevel, wherein the first performance level causes a finite water flow inthe hot water line which is below an operation threshold value of thetankless heater device, and wherein the second performance level ishigher than the first performance level and is above the operationthreshold value of the tankless heater device.

The first portion of the hot water line is a hot water supply line. Thesecond portion of the hot water line is a hot water recirculation line.With the present invention, water can be circulated at the firstperformance level with constant low speed. This ensures that there willbe no cold bursts coming out of the hot water faucet part. Such coldbursts can be caused by in particular spatially uneven cooling of waterstaying in the hot water line. In particular, even if the first portionor part of the first portion of the hot water line is running in orunder a concrete slab, such cold bursts are avoided. The temperature inthe hot water line will vary only in a minimum manner. When switching tothe second performance level, a quick reheating of water in the hotwater line is brought about.

In particular, the heating operation of the tankless heater device isflow rate controlled and the operation threshold value is a thresholdflow rate value. When, for example, a hot water faucet part is opened arelatively high flow rate is reached resulting in heating operation ofthe tankless heater device. Even when the faucet device is closed, withthe present invention by switching to the second performance level, thecirculatory pump can bring the tankless heater device into heatingoperation for reheating water in the complete hot water line at highspeed.

It is advantageous if the circulatory pump has a third performance levelat which the flow rate in the hot water line is substantially zero.Such, for times for which no hot water consumption is expected (like atnighttimes) water recirculation in the hot water line can be switchedoff.

In particular, the circulatory pump comprises a control device whichswitches between the first performance level and the second performancelevel. Such, a closed control loop can be provided.

The control device is coupled to at least one of (i) at least one sensorof the circulatory pump, and (ii) at least one sensor of the tanklessheater device, wherein depending on the received signals from the atleast one sensor either the first performance level or the secondperformance level is switched to.

In particular, the at least one sensor is a temperature sensor. Such, bymeasuring the temperature in the hot water line or in the tanklessheater device, control signals for the circulatory pump can be gained.

In one embodiment, the circulatory pump comprises a thermostat. Thisthermostat can be used for deciding whether the first performance levelor the second performance level is to be switched to.

In one embodiment, the control device switches operation of thecirculatory pump from the first performance level to the secondperformance level when a temperature measured by the at least onetemperature sensor is or falls under a first temperature threshold valueand switches from the second performance level to the first performancelevel when the measured temperature is above or passes a secondtemperature threshold value. Such, an automatic adjustment of the waterdelivery system is achieved avoiding cold water bursts. The firsttemperature threshold and the second threshold temperature arepreferably different.

It is advantageous if the second temperature threshold value is higherthan the first temperature threshold value. Such, a hysteresis isprovided.

In one embodiment, a timer is provided for controlling the time betweenswitching processes. Such, especially when combined with a hysteresis oftemperature thresholds, a recommended minimum running time betweenswitching processes and/or a minimum switch-off temperature of thetankless heater device can be considered, in particular for avoidingcondensation in a heat exchanger.

In one embodiment, the circulatory pump comprises an interface devicefor signals or data from the tankless heater device. Such, the tanklessheater device can provide data and/or signals in a wired manner orwireless manner to the circulatory pump. For example, temperaturesignals provided from the tankless heater device to the circulatory pumpcan be used for switching to the first performance level or secondperformance level of the circulatory pump. In one embodiment,performance levels of the circulatory pump can be adjusted or set by thetankless heater device.

In particular, the tankless heater device comprises a flow meter. Thisflow meter is used by a corresponding control unit of the tanklessheater device for switching to heating operation mode from a non-heatingoperation mode or vice versa.

It is advantageous when a time of the day timer is provided that isconnected to or is part of the circulatory pump for setting a thirdperformance level which is a zero flow level. Such, a timing scheme canbe provided which switches off the circulatory pump completely for timesfor which no hot water consumption is expected (like, for nighttimes).

The tankless heater device may comprise an interface device forproviding data or signals to the circulatory pump. Such, data or signalscan be transferred in a wired or wireless manner from the tanklessheater device to the circulatory pump.

The tankless heater device might comprise a control device for settingor adjusting at least one of the first performance level and the secondperformance level at the circulatory pump. Such, the value of theseperformance levels can be provided by the tankless heater device insteadof being internal settings of the circulatory pump. Such, it is possibleto adapt non-standard systems automatically. For example, non-standardsystems in terms of pipe resistances can be used as water deliverysystems in accordance with the invention.

In one embodiment, a flow control valve is arranged in the hot waterline between the circulatory pump and the tankless heater device. Thisflow control valve might be used to further reduce a low performancelevel. If the hydraulic resistance of the corresponding lines is verylow it might happen that the tankless heater device starts heatingalready at quite low circulating pump performances. The flow controlvalve allows reducing the flow rate.

In particular, the second portion of the hot water line is arecirculation line for hot water.

In a further embodiment of the invention, a method for making hot wateravailable in a domestic hot water installation is provided, saiddomestic hot water installation comprising a tankless heater device, ahot water line, a cold water line, at least one faucet device connectedto the cold water line and the hot water line, and a circulatory pumparranged in the hot water line. The method comprises setting a prefixedfirst performance level and a prefixed second performance level at thecirculatory pump, wherein the first performance level causes a finitewater flow in the hot water line which is below an operation thresholdvalue of the tankless heater device and wherein the second performancelevel is higher than the first performance level and above the operationthreshold value of the tankless heater device, switching to the firstperformance level of the circulatory pump for providing a low speedcirculation of hot water when the temperature of the hot water in thehot water line is above a temperature threshold value, and switching tothe second performance level when the temperature is below a temperaturethreshold value.

In particular, the temperature in the hot water line is measured at atleast one of the circulatory pump and the tankless heater device.

It is advantageous when the heating operation of the tankless heaterdevice is flow controlled and the operation threshold value is a flowrate threshold value.

The invention is described herein, by way of example only, withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a hot water delivery system in accordancewith an embodiment of the present invention;

FIG. 2 is a schematic diagram showing the flow rate as a function oftime for the hot water delivery system of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

A water delivery system in accordance with the present invention, whichis schematically shown in FIG. 1 and designated by 10, comprises atankless heater device 12. The tankless heater device 12 is preferably aunit which can be fixed in a domestic environment. For example, thisunit can be fixed to a wall or to a floor in the domestic environment.

The tankless heater device 12 comprises an outlet 14 (for hot water) andan inlet 16. Between the inlet 16 and the outlet 14 one or more waterlines 18 are arranged. Such a water line or such water lines 18 are partof a heat exchanger 20. For example, the water line or water lines 18comprise a coil part 22. A heater 24 is arranged in proximity or at thecoil part 22. In an operation mode of the tankless heater device 12, theheater 24 heats water running through the coil part 22. The heater 24is, e.g., an electric heater arranged at the coil part 22, or a burner.A flame front of such a burner heats the coil part 22.

The tankless heater device 12 comprises a control unit 26 which controlsoperation of the tankless heater device 12.

The water delivery system 10 comprises (at least one) hot water line 28.This hot water line 28 is connected to the outlet 14 of the tanklessheater device 12. The hot water line 28 is further connected to theinlet 16 of the tankless heater device 12. Such, the hot water line 28provides a circulatory loop 30 in which water can circulate from theoutlet 14 to the inlet 16 of the tankless heater device 12 and throughthe water line or water lines 18 of the tankless heater device 12.

In the hot water line 28 a circulatory pump 32 is arranged. Thiscirculatory pump 30, when in an operating mode, drives the flow of waterthrough the loop 30.

Further, the water delivery system comprises (at least one) cold waterline 34.

In an embodiment, a connection 36 is provided between the cold waterline 34 and a hot water line 28. Via the connection 36, water isprovided to the hot water line system.

The water delivery system 10 comprises at least one faucet device 38.This faucet device 38 is, e.g., arranged at a sink.

The faucet device 38 has a hot water faucet part 40 and a cold waterfaucet part 42. The hot water faucet part 40 is connected to the hotwater line 28. Via the hot water faucet part 40 hot water can be tapped.The cold water faucet part 42 is connected to the cold water line 34.Via the cold water faucet part 42 cold water can be tapped.

The hot water line 28 has a first portion 44 running between the outlet14 of the tankless heater device 12 and the faucet device 38 or, if aplurality of faucet devices are provided, the last faucet device whichhas in a flow direction 46 of hot water from the tankless heater device12 the largest distance from the outlet 14. This first portion 44 is ahot water supply line.

Further, the hot water line 28 comprises a second portion 48 which runsbetween the faucet device 38 (or the last faucet device 38) and theinlet 16. This second portion 48 is a recirculatory line.

The circulatory pump 32 is arranged in the second portion 48 of the hotwater line 28. Namely, the circulatory pump 32 is arranged after thelast faucet device 38 in the flow direction 46.

In an embodiment, a flow control valve 50 is arranged in the secondportion 48 of the hot water line 28. Preferably, the flow control valve50 is arranged between the circulatory pump 32 and the inlet 16. Betweenthe flow control valve 50 and the circulatory pump 32 a non-return valve51 is arranged.

In one embodiment, the circulatory pump 32 comprises a temperaturesensor 52 or a thermostat with a temperature sensor. This temperaturesensor 52 measures the temperature in the second portion 58 of the hotwater line 28 at the circulatory pump 32. Such, a pump unit is providedcomprising a pumping part and a thermostat or temperature sensor 52.

The tankless heater device 12 is arranged at a distance from the faucetdevice 38 (or the first faucet device 38 in the flow direction 46 afterthe outlet 14). Often, this distance is significant. For example, in adomestic water delivery system 10 the tankless heater device 12 isarranged in a garage and one or more faucet devices 38 are arranged inthe living area or areas of a house. When the circulatory pump 32 is notoperating, water does not flow in the hot water line 28. If thecirculatory pump 32 is operated during non-tapping times, water can becirculated in the loop 30 driven by the circulatory pump 32.

In particular, the tankless heater device 12 is controlled by the waterflow in the hot water line 28. For this, a flow meter 54 is provided.The flow meter 54 is arranged in the tankless heater device 12 in awater line 18. If water is circulated at a high enough speed (measuredby the flow meter 54) the heater 24 of the tankless heater device 12 isactive. The control unit 26 registers signals from the flow meter 54 andcontrols the heater 24.

Principally, water in the hot water line 28 is heated up to a specifictemperature. If this temperature, measured by the temperature sensor 52,is reached, the circulatory pump 32 is turned off and the water in thehot water line 28 cools down again.

There can arrive the following problem, which is also called the slabproblem: The first portion 44 of the hot water line 28 can be at leastpartially embedded in or under concrete. There, the water cools downfaster than outside this region. This might result in that thetemperature measured at the temperature sensor 52 indicates that arecirculation is not necessary, that is that the circulatory pump 32 hasnot to be operated.

If, for example, a user of the water delivery system 10 takes a shower,then the cold water that has been in the first portion 44 of the hotwater line 28 will come out at the corresponding hot water faucet part40 as a cold water burst.

U.S. Pat. No. 7,832,421 B2 describes a method to counteract the slabproblem by transporting water from a hot water source with asubstantially permanent throughput with at most periodic pause times andsaid pause times having a length selected to prevent cooling of water inthe hot water line.

With a tankless heater device 12, such a method is usually not workablesince hot water cannot be drawn from a hot water tank and usually thetankless heater device 12 does not work or does not work in an effectivemanner at very low flow rates.

In accordance with the present invention, the circulatory pump 32comprises a fixed (preset) first performance level P₁ and a fixed(preset) second performance level P₂. The first performance levelconstitutes a finite low speed circulation of hot water in the loop 30.This is schematically shown in the diagram of FIG. 2. The flow ratecorresponding to the first performance level P₁ of hot water in the loop30 is above zero. However, this flow rate is below the threshold flowrate of the tankless heater device 12. Such, if the circulatory pump 32is operated with the first performance level P₁, a permanent throughputof water in the hot water line 28 takes place but without active heatingoperation of the heater 24 of the tankless heater device 12.

The threshold value flow rate is shown in FIG. 2 with the referencenumeral 56.

The second performance level P₂ is higher than the first performancelevel P₁. The corresponding flow rate is above the threshold flow rate56. This means, when the circulatory pump 32 is operated at the secondperformance level P₂, the flow rate controlled heating of the tanklessheater device 12 takes place, i.e., the heater 24 is operative and heatswater going through the coil part 22.

The circulatory pump 32 comprises a control device 58 which controlsoperation of the circulatory pump 32 and in particular, whether the pumpis operated at the first performance level P₁ or the second performancelevel P₂. The performance levels P₁ and P₂ are switching states of thecirculatory pump 32, said switching states being controlled by thecontrol device 58.

The circulatory pump 32 also has a third performance level P₃ which is azero level. In the zero level, basically no water flow in the hot waterline 28 takes place (outside tapping times). This is indicated in FIG. 2with the reference numeral 60. Such a zero flow 60 can be provided atday times or night times when no hot water tapping is expected.

The circulatory pump 32 (or the tankless heater device 12) comprises forthis a timer 62 which is a time of the day timer 62. This timer 62 isconnected to the control device 58 directly (in particular, via hardwareconnection) if the timer 62 is part of the circulatory pump 32. If thetimer 62 is part of the tankless heater device 12, it is connected tothe control device 58 in a signal effective manner so that signals canbe transferred to the control device 58 of the circulatory pump 32.

With the timer 62, non-operative times of the circulatory pump 32 can bepreset.

In one embodiment, the control device 58 uses the temperature signals ofthe temperature sensor 52 to decide whether the circulatory pump 32 isto be operated at the first performance level P₁ or at the secondperformance level P₂ outside the zero flow regime. If the temperaturemeasured by the temperature sensor 52 falls below a first temperaturethreshold value and the pump is operated at the first performance levelP₁, it is switched to the second performance level P₂. As a result ofthat, the flow rate operated tankless heater device 12 is switched to aheating mode and the temperature of the water in the hot water line 28rises in a quick manner.

If the temperature measured by the temperature sensor 52 reaches asecond temperature threshold value, the performance level of thecirculatory pump 32 is switched from P₂ to P₁ since no further heatingis required. As a result, water in the hot water line 28 will cool down(until the lower temperature threshold value is reached). In anexemplary embodiment, the second temperature threshold value is higherthan the first temperature threshold value so that a hysteresis isprovided.

As an example, the first temperature threshold value is about 40° C. orabout 100° F. and the second temperature threshold value is about 50° C.or about 120° F.

In one embodiment, a timer is provided (which can be part of the controldevice 58) for taking into consideration a recommended minimum runningtime between switching states and/or minimum a switch-off temperature ofthe tankless heater device 12. Such, condensation in the heaterexchanger 20 can be avoided.

Instead of the temperature sensor 52, a thermostat of the circulatorypump 32 can be used for providing signals to the control device 58 todecide about switching between the performance levels P₁ and P₂.

With the present invention, the comfort level of the water deliverysystem 10 is improved. Outside zero flow times, the constant low speedcirculation of water in the loop 30 with the circulatory pump 32 beingoperated at the first performance level P₁ ensures that there will be nocold bursts coming out of the hot water faucet parts 40; the temperatureof hot water in the first portion 44, which is a hot water supply line,and in the second portion 48, which is a recirculation line, varies onlyat a low amount. If a switching to the higher performance level P₂ takesplace, the water in the loop 30 is reheated in a quick manner.

In one embodiment, the tankless heater device 12 comprises an interfacedevice 64. This interface device 64 is used for transmitting (in a wiredor non-wired manner) data and/or signals to the circulatory pump 32. Forreceiving such data signals, the circulatory pump 32 comprises acorresponding interface device 66, which is connected in a signaleffective manner to the control device 58.

For example, the tankless heater device 12 comprises a temperaturesensor 68 and the temperature signals of this temperature sensor areused by the control device 48 of the circulatory pump 32 for switchingbetween the first performance level P₁ and the second performance levelP₂.

Also, the interface device 64 can be used to set the prefixedperformance levels P₁ and P₂ via the tankless heater device 12. Forexample, a pulse width modulation speed control of the circulatory pump32 is used. Such, an automatic adaptation to non-standard systems (interms of water pipe resistance) can be accomplished.

The flow control valve 50 can be advantageous if the hydraulicresistance in the hot water line 28 is low. As a result, the heater 24of the tankless heater device 12 might start heating operation alreadyat low performance levels of the circulatory pump 32. With the flowcontrol valve 50, the flow rate can be adapted and a lower performancelevel can be further reduced.

LIST OF REFERENCE NUMERALS

-   10 water delivery system-   12 tankless heater device-   14 outlet-   16 inlet-   18 water line-   20 heat exchanger-   22 coil part-   24 heater-   26 control unit-   28 hot water line-   30 circulatory loop-   32 circulatory pump-   34 cold water line-   36 connection-   38 faucet device-   40 hot water faucet part-   42 cold water faucet part-   44 first portion-   46 flow direction-   48 second portion-   50 flow control valve-   51 non-return valve-   52 temperature sensor-   54 flow meter-   56 threshold flow rate-   58 control device-   60 zero flow-   62 timer-   64 interface device-   66 interface device-   68 temperature signal

1. Water delivery system, comprising: at least one faucet device with acold water faucet part and a hot water faucet part; a cold water line tothe at least one faucet device; a tankless heater device for heatingwater; a hot water line having a first portion running from an outlet ofthe tankless heater device to the at least one faucet device and havinga second portion running from the at least one faucet device to an inletof the tankless heater device; and a circulatory pump arranged in thesecond portion of the hot water line; wherein the circulatory pump has aprefixed first performance level and a prefixed second performancelevel; wherein the first performance level causes a finite water flow inthe hot water line which is below an operation threshold value of thetankless heater device; and wherein the second performance level ishigher than the first performance level and is above the operationthreshold value of the tankless heater device.
 2. Water delivery systemin accordance with claim 1, wherein heating operation of the tanklessheater device is flow rate controlled and the operation threshold valueis a threshold flow rate value.
 3. Water delivery system in accordancewith claim 1, wherein the circulatory pump has a third performance levelat which the flow rate in the hot water line is substantially zero. 4.Water delivery system in accordance with claim 1, wherein thecirculatory pump comprises a control device which switches between thefirst performance level and the second performance level.
 5. Waterdelivery system in accordance with claim 4, wherein the control deviceis coupled to at least one of (i) at least one sensor of the circulatorypump, and (ii) at least one sensor of the tankless heater device,wherein depending on the received signals from the at least one sensoreither the first performance level or the second performance level isswitched to.
 6. Water delivery system in accordance with claim 5,wherein the at least one sensor is a temperature sensor.
 7. Waterdelivery system in accordance with claim 5, wherein the circulatory pumpcomprises a thermostat.
 8. Water delivery system in accordance withclaim 6, wherein the control device switches from the first performancelevel to the second performance level when a temperature measured by theat least one temperature sensor is or falls under a first temperaturethreshold value and switches from the second performance level to thefirst performance level when the measured temperature is above or passesa second temperature threshold value.
 9. Water delivery system inaccordance with claim 8, wherein the second temperature threshold valueis higher than the first temperature threshold value.
 10. Water deliverysystem in accordance with claim 8, wherein a timer is provided forcontrolling the time between switching processes.
 11. Water deliverysystem in accordance with claim 1, wherein the circulatory pumpcomprises an interface device for signals or data from the tanklessheater device.
 12. Water delivery system in accordance with claim 1,wherein the tankless heater device comprises a flow meter.
 13. Waterdelivery system in accordance with claim 1, wherein a time of the daytimer connected to or being part of the circulatory pump is provided forsetting a third performance level which is a zero flow level.
 14. Waterdelivery system in accordance with claim 1, wherein the tankless heaterdevice comprises an interface device for providing data or signals tothe circulatory pump.
 15. Water delivery system in accordance with claim1, wherein the tankless heater device comprises a control device forsetting or adjusting at least one of the first performance level and thesecond performance level at the circulatory pump.
 16. Water deliverysystem in accordance with claim 1, wherein a flow control valve isarranged in the hot water line between the circulatory pump and thetankless heater device.
 17. Water delivery system in accordance withclaim 1, wherein a connection between the hot water line and the coldwater line is provided.
 18. Water delivery system in accordance withclaim 1, wherein the second portion of the hot water line is arecirculation line for hot water.
 19. Method for making hot wateravailable in a domestic hot water installation, said domestic hot waterinstallation comprising a tankless heater device, a hot water line, acold water line, at least one faucet device connected to the cold waterline and the hot water line, and a circulatory pump arranged in the hotwater line, comprising: setting a prefixed first performance level and aprefixed second performance level at the circulatory pump, wherein thefirst performance level causes a finite water flow in the hot water linewhich is below an operation threshold value of the tankless heaterdevice and wherein the second performance level is higher than the firstperformance level and above the operation threshold value of thetankless heater device; switching to the first performance level of thecirculatory pump for providing a low speed circulation of hot water whenthe temperature of the hot water in the hot water line is above atemperature threshold value; and switching to the second performancelevel when the temperature is below a temperature threshold value. 20.Method in accordance with claim 19, wherein the temperature in the hotwater line is measured at at least one of the circulatory pump and thetankless heater device.
 21. Method in accordance with claim 19, whereinheating operation of the tankless heater device is flow controlled andthe operation threshold value is a flow rate threshold value.